The present invention relates to a one-dimensional or two-dimensional laser diode array, and particularly to a structure for mounting one or a plurality of laser diodes on a monolithic substrate as a subassembly of a working laser device, and to a method of fabrication of such a subassembly. The invention has application in many areas in which high power semiconductor laser arrays are used, including satellite communications, directed energy applications, remote sensing of atmospheric conditions, range finding, and isotope separation. Other applications include optical recording, computing, laser machining, level sensing, and remote sensing.
While there have been substantial improvements over the last few years in performance and reliability of laser diode materials, such as AlGaAs, there have not been corresponding improvements in the area of packaging technologies for laser diodes. To date, existing first generation laser packaging techniques have utilized either soft solder (In) or Sn/Au soldering systems on Cu, BeO, Thermkon (tm), or even diamond substrates. Although these techniques are adequate for fabricating engineering prototypes, they are not suitable for high volume fabrication of reliable, low cost, one-dimensional (1D) and two-dimensional (2D) laser arrays.
One example of a laser packaging technique known to the inventor of the present application, the inventor having participated in the development of that technique, is known as the "Rack & Stack" assembly process. According to this process, individual 1D subarrays are assembled, and are mounted on a backplane to form a 2D array. The number of parts involved makes it very difficult to achieve high volume production, particularly since the number of assembly steps is large, and yield has tended to be relatively low. Many of the individual assembly steps require careful alignment of the individual subarrays, contributing to longer required assembly time and lower yield. Further, the 1D subarrays used are not reworkable; if a flaw is discovered in a part of the subarray, the entire subarray must be scrapped, as individual laser diodes in the subarray cannot be replaced.